Treatments of Effect Sizes and Statistical Significance Tests in Textbooks

Abstract

The dialog surrounding effect sizes and statistical significance tests often places the two ideas into separate camps amid controversy. In light of recommendations by the Task Force on Statistical Inference and the fifth edition of the American Psychological Association Publication Manual calling for the reporting of effect sizes, a review of treatments of effect sizes in textbooks may be quite timely. This study reviews textbooks published since 1995 and as regards treatments of effect sizes and statistical significance tests. Of The textbooks examined, every textbook ( n = 89) included the topic of statistical significance testing (2,248 pages), whereas only a little more than two thirds of the textbooks ( n = 60) included information on effect sizes (789 pages).